Question

What would be the effect on the slope of the calibration curve if you were to choose a wavelength to do the analysis that was 50 nm longer than the wavelength selected in the experiment?

Answer 1

Ans. Energy of a photon is given by-

                        E = hv            - equation 1

; where, h = Plank’s constant = 6.626 x 10^-34 Js   ; v = frequency of photon   

Or, E = h x (c / l)      - equation 2

                        Where, c = speed of light    ; l = wavelength

# Following equation 2, the energy of photon is inversely proportional to wavelength. That is, longer is the wavelength, lower would be its energy.

# Using a longer wavelength (50 nm longer than the optimum value), less energy would be available to the specified chemical species (that absorbs light at given wavelength).

So, a lower fraction of the specified chemical species would absorb the light of longer wavelength.

That is, the molecules would absorb less than the optimal absorption.

So, the absorption values of aliquots are relatively lower than the optimum values. So, plotting absorbance values to the respective concentration of aliquots would give the liner with lower (less steep) slope.

In summary, the slope of graph would be lower than the slope at optimum wavelength.